The invention is based on a device for operating a gas discharge lamp having a power supply circuit which makes available an alternating voltage or an alternating current of a predetermined period duration for the supply of the gas discharge lamp with a predetermined power. From DE-A 37 15 162.2, a circuit arrangement for operating a gas discharge lamp is known comprising a voltage transformer that converts the energy made available by a direct current source to an alternating voltage of appropriate level and frequency. At control inputs, the voltage transformer receives control signals derived from the lamp voltage and from the lamp current to supply the gas discharge lamp with a predetermined electrical power. During the pole-changing process of the alternating voltage, an instantaneous power reduction occurs in the gas discharge lamp, which power reduction can lead to a short-time reduction of the arc. A sufficiently high operating frequency, which may be, for example, at a few 100 Hertz, ensures that the arc does not go out entirely during the short current zero. The required voltage after the pole-changing process for the maintenance of the arc during operation at normal rating corresponds to the normal burning voltage of the gas discharge lamp. A reduction of the electrical power supplied to the gas discharge lamp results in a total interruption of the arc during the pole-changing process. The power supply circuit must be able to come up with the necessary reignition voltage after the pole-changing process. A reduction of the electrical power supplied to the gas discharge lamp is therefore possible to the same extent that the power supply circuit is able to come up with the reignition voltage.
It is the object of the invention to provide a device for operating a gas discharge lamp which ensures a reliable operation of the gas discharge lamp in an operating phase with reduced power.